Can you sell Blankos?

Can you please clarify for me, are Blankos digital collectibles that can be bought and sold? If so, is there a marketplace or platform where they can be exchanged? I'm interested in understanding the process of selling Blankos, as I have some in my possession and am considering liquidating them. Additionally, are there any restrictions or fees associated with the sale of Blankos that I should be aware of? I'd appreciate any information you can provide on this matter.